1. Technical Field
The present subject matter relates in general to data receivers and more particularly, to decision feedback equalizers used in receivers.
2. Background Information
In many digital communication systems (e.g., network switches), a source generates digital information, such as data, audio, or video, and transmits such information to one or more receivers. The digital information bits may be divided into blocks that define a discrete alphabet of symbols. These symbols may be used to modulate a carrier's frequency, amplitude or phase.
The digital bit stream is transmitted across a communication medium (e.g., a copper backplane) and detected by a receiver. Such communication media (also referred to as the “channel”) may cause the transmitted signal to become distorted as it propagates across the channel. As a result, symbols may smear across multiple symbol boundaries, i.e., one symbol may bleed over into other symbols. This phenomenon is referred to as inter-symbol interference (“ISI”). Further, noise may be added to the received signal from transmitter and receiver component imperfections, and from other sources along the propagation path.
The receiver attempts to receive and correctly reproduce the originally transmitted bit stream. That is, a transmitted logic “1” should be accurately determined to be a “1” by the receiver and, similarly, a transmitted logic “0” should be determined to be a “0” upon reception. Some receivers may include an equalizer to mitigate the effects of ISI and noise caused by the channel and other effects. Because the exact channel characteristics may not be known apriori at the receiver, the equalizer may be implemented with adaptive methods. Data rates continue to trend upward and are approaching the upper limit of what is possible with presently preferred types of semiconductor technology (e.g., CMOS). Further, many applications benefit from, if not demand, lower power consumption equipment. The upward trend in data rates in the face of expectations for lower power consumption devices imposes considerable design challenges for faster, lower power receivers.